1. Field of the Invention
The present invention relates to an internal combustion engine and a method of operation thereof and, more particularly, to an internal combustion engine equipped with a fuel reforming system and an exhaust gas recirculation system (EGR system) and a method for the operation of the engine of the type specified.
2. Description of the Prior Art
Internal combustion engines equipped with fuel reforming systems have heretofore been proposed to simultaneously reduce kinds of harmful components of engine exhaust gases and to improve the engine drivability.
The internal combustion engine of this type has been operated by the supply of combustible gases at a lean air-fuel ratio such as from 18 to 22, for example. The combustible gases consisted of a mixture of air and gasoline and a reformed gaseous mixture produced by the reformation of a hydrocarbon fuel, such as gasoline, or an alcohol, such as methanol or ethanol. The engine was operated in such a manner that the reformed gaseous mixture was always supplied into the engine regardless of the engine operating conditions. In the case where a hydrocarbon fuel was used to produce a reformed gaseous mixture, an energy loss occurred in the fuel reforming process. This manner of engine operation, therefore, has not much contributed to the improvement in the total fuel consumption rate.
The use of an alcohol to produce a reformed combustible gaseous mixture is advantageous in that alcohol is easy to reform and energy loss hardly occurs. However, difficulties have been found in the use of alcohols that gaseous combustible mixtures obtained by the reformation of alcohols are more expensive than other kinds of reformed gaseous mixtures and the calorie per unit volume of an alcohol is lower than that of gasoline with a resultant increase in the fuel consumption.